In known injectors, for example diesel piezo common-rail injectors, an injection valve for injecting fuel into the combustion chamber of the cylinder head is actuated by a piezoactuator. As a result of a voltage being applied to the piezoactuator or as a result of the electrodes of a piezoactuator being charged with a charge current pulse, the piezoactuator experiences a change in length. This change in length is transmitted as an operating stroke to a valve element of the injection valve. In order to close the injection valve, the electrodes of the piezoactuator are discharged with a corresponding discharge current pulse. The change in length is thereby reversed and the movement of the piezoactuator transmitted to the valve element of the injection valve in order to close the valve. These changes in length of the piezoactuator take place in a highly dynamic fashion and generate acceleration forces and mechanical oscillations which, in the installed state on a cylinder head, are audibly transmitted to the injector and the cylinder head. This noise which is caused by the piezoactuator is frequently felt to be disruptive, in particular if it predominates over the combustion noises in the idling mode of the engine.
In the known piezo diesel common-rail systems, attempts have been made to adapt the current profile used for actuating the piezoactuator in such a way that the particularly disruptive, relatively high frequency components of the noise are reduced. For this purpose, for example the charge time of the piezoactuator was increased from 100 microseconds to approximately 180 microseconds. However, in addition to the desired reduction of the disruptive frequency components, the accuracy of the injection quantities, in particular in the very small quantity range, was also adversely affected. Screens, for example in the form of a plastic cover, were introduced as further measures, but said screens only act in the direction of the positioning of the corresponding screen element. The application of the oscillations to the cylinder head or engine and therefore the generation of noise cannot be eliminated with these measures. A further disadvantage of these screening measures is the associated high cost.